关于友元函数的问题
各位大虾，友元函数是不是不能放在类外实现啊。为什么我每次把友元函数放在类外实现，都编译时都会产生错误能。比如说我这样一段代码：#ifndef stH
#define stH
#include<iostream>
using namespace std;
class stack
{
private:
static int maxsize;
int top;
int *data;
public:
stack();
void push(int item);
int pop();
int peek();
void stackEmpty()const;
void stackFull()const;
friend ostream &operator<<(ostream &out,stack &st);
};
#endif
如果我把ostream &operator<<(ostream &out,stack &st);
放到类外实现就会产生错误。这个文件我是放在一个保存在一个头文件中的。我实现的时候放在了一个
.CPP文件中，这样可以吗？
问题点数：0、回复次数：2Top
1 楼zhouyong0371（小周周）回复于 2004-12-03 15:15:56 得分 0
#include<iostream>
using namespace std;
class stack
{
private:
static int maxsize;
int top;
int *data;
public:
stack(){
top = 0;
data = new int[11];
};
~stack(){
delete [] data;
};
void push(int item){
*(data + top) = item;
top++;
};
int pop(){
top--;
return *(data + top);
};
int peek(){
return *(data + top - 1);
};
void stackEmpty()const{
};
void stackFull()const{
};
//friend ostream &operator<<(ostream &out,stack &st);
};
int stack::maxsize = 10;
ostream &operator<<(ostream &out, stack &st)
{
return out << st.peek();
}
void main()
{
stack s;
s.push(10);
cout << s << endl;
}Top
2 楼wwxsoft（婉儿）回复于 2004-12-03 15:43:24 得分 0
友元函数可以放到类外来实现得，比如下面一个程序，就是友元函数放到类外来实现得
#include <iostream>
#include <stdlib.h>
using namespace std;
class complex
{
public:
complex(double r=0.0,double i=0.0){real=r;imag=i;}
friend complex operator +(complex c1,complex c2);
friend complex operator -(complex c1,complex c2);
void display();
private:
double real;
double imag;
};
void complex::display()
{
cout<<"("<<real<<","<<imag<<")"<<endl;
}
complex operator +(complex c1,complex c2)
{
return complex(c1.real+c2.real,c1.imag+c2.imag);
}
complex operator -(complex c1,complex c2)
{
return complex(c1.real-c2.real,c1.imag-c2.imag);
}
int main(int argc, char *argv[])
{
complex c1(5,4),c2(2,10),c3;
cout<<"c1=";c1.display();
cout<<"c2=";c2.display();
c3=c1+c2;
cout<<"c3=c1+c2=";c3.display();
c3=c1-c2;
cout<<"c3=c1-c2";c3.display();
system("PAUSE");
return 0;
}Top
